Commit 925ad0c2 authored by Boris Brezillon's avatar Boris Brezillon
Browse files

drm/panthor: Provide a custom dma_buf implementation 



Before we introduce cached CPU mappings, we want a dma_buf
implementation satisfying synchronization requests around CPU
accesses coming from a dma_buf exported by our driver. Let's
provide our own implementation relying on the default
gem_shmem_prime helpers designed for that purpose.

v5:
- New patch

v6:
- Collect R-b

v7:
- Hand-roll the dma_buf sync/import logic (was previously done by
  generic prime/shmem helpers)

v8:
- No changes

Reviewed-by: default avatarSteven Price <steven.price@arm.com>
Link: https://patch.msgid.link/20251208100841.730527-2-boris.brezillon@collabora.com


Signed-off-by: default avatarBoris Brezillon <boris.brezillon@collabora.com>
parent bcd752c7

drivers/gpu/drm/panthor/panthor_drv.c

+1 −0
Original line number Diff line number Diff line
@@ -1623,6 +1623,7 @@ static const struct drm_driver panthor_drm_driver = { 


	.gem_create_object = panthor_gem_create_object,

	.gem_prime_import_sg_table = drm_gem_shmem_prime_import_sg_table,

	.gem_prime_import = panthor_gem_prime_import,

#ifdef CONFIG_DEBUG_FS

	.debugfs_init = panthor_debugfs_init,

#endif

drivers/gpu/drm/panthor/panthor_gem.c

+117 −1
Original line number Diff line number Diff line
@@ -202,14 +202,130 @@ panthor_kernel_bo_create(struct panthor_device *ptdev, struct panthor_vm *vm, 
	return ERR_PTR(ret);

}



static struct sg_table *

panthor_gem_prime_map_dma_buf(struct dma_buf_attachment *attach,

			      enum dma_data_direction dir)

{

	struct sg_table *sgt = drm_gem_map_dma_buf(attach, dir);



	if (!IS_ERR(sgt))

		attach->priv = sgt;



	return sgt;

}



static void

panthor_gem_prime_unmap_dma_buf(struct dma_buf_attachment *attach,

				struct sg_table *sgt,

				enum dma_data_direction dir)

{

	attach->priv = NULL;

	drm_gem_unmap_dma_buf(attach, sgt, dir);

}



static int

panthor_gem_prime_begin_cpu_access(struct dma_buf *dma_buf,

				   enum dma_data_direction dir)

{

	struct drm_gem_object *obj = dma_buf->priv;

	struct drm_device *dev = obj->dev;

	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);

	struct dma_buf_attachment *attach;



	dma_resv_lock(obj->resv, NULL);

	if (shmem->sgt)

		dma_sync_sgtable_for_cpu(dev->dev, shmem->sgt, dir);



	if (shmem->vaddr)

		invalidate_kernel_vmap_range(shmem->vaddr, shmem->base.size);



	list_for_each_entry(attach, &dma_buf->attachments, node) {

		struct sg_table *sgt = attach->priv;



		if (sgt)

			dma_sync_sgtable_for_cpu(attach->dev, sgt, dir);

	}

	dma_resv_unlock(obj->resv);



	return 0;

}



static int

panthor_gem_prime_end_cpu_access(struct dma_buf *dma_buf,

				 enum dma_data_direction dir)

{

	struct drm_gem_object *obj = dma_buf->priv;

	struct drm_device *dev = obj->dev;

	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);

	struct dma_buf_attachment *attach;



	dma_resv_lock(obj->resv, NULL);

	list_for_each_entry(attach, &dma_buf->attachments, node) {

		struct sg_table *sgt = attach->priv;



		if (sgt)

			dma_sync_sgtable_for_device(attach->dev, sgt, dir);

	}



	if (shmem->vaddr)

		flush_kernel_vmap_range(shmem->vaddr, shmem->base.size);



	if (shmem->sgt)

		dma_sync_sgtable_for_device(dev->dev, shmem->sgt, dir);



	dma_resv_unlock(obj->resv);

	return 0;

}



static const struct dma_buf_ops panthor_dma_buf_ops = {

	.attach = drm_gem_map_attach,

	.detach = drm_gem_map_detach,

	.map_dma_buf = panthor_gem_prime_map_dma_buf,

	.unmap_dma_buf = panthor_gem_prime_unmap_dma_buf,

	.release = drm_gem_dmabuf_release,

	.mmap = drm_gem_dmabuf_mmap,

	.vmap = drm_gem_dmabuf_vmap,

	.vunmap = drm_gem_dmabuf_vunmap,

	.begin_cpu_access = panthor_gem_prime_begin_cpu_access,

	.end_cpu_access = panthor_gem_prime_end_cpu_access,

};



static struct dma_buf *

panthor_gem_prime_export(struct drm_gem_object *obj, int flags)

{

	struct drm_device *dev = obj->dev;

	struct dma_buf_export_info exp_info = {

		.exp_name = KBUILD_MODNAME,

		.owner = THIS_MODULE,

		.ops = &panthor_dma_buf_ops,

		.size = obj->size,

		.flags = flags,

		.priv = obj,

		.resv = obj->resv,

	};



	/* We can't export GEMs that have an exclusive VM. */

	if (to_panthor_bo(obj)->exclusive_vm_root_gem)

		return ERR_PTR(-EINVAL);



	return drm_gem_prime_export(obj, flags);

	return drm_gem_dmabuf_export(dev, &exp_info);

}



struct drm_gem_object *

panthor_gem_prime_import(struct drm_device *dev,

			 struct dma_buf *dma_buf)

{

	struct drm_gem_object *obj = dma_buf->priv;



	if (dma_buf->ops == &panthor_dma_buf_ops && obj->dev == dev) {

		/* Importing dmabuf exported from our own gem increases

		 * refcount on gem itself instead of f_count of dmabuf.

		 */

		drm_gem_object_get(obj);

		return obj;

	}



	return drm_gem_prime_import(dev, dma_buf);

}



static enum drm_gem_object_status panthor_gem_status(struct drm_gem_object *obj)

drivers/gpu/drm/panthor/panthor_gem.h

+4 −0
Original line number Diff line number Diff line
@@ -149,6 +149,10 @@ panthor_gem_create_with_handle(struct drm_file *file, 
void panthor_gem_bo_set_label(struct drm_gem_object *obj, const char *label);

void panthor_gem_kernel_bo_set_label(struct panthor_kernel_bo *bo, const char *label);



struct drm_gem_object *

panthor_gem_prime_import(struct drm_device *dev,

			 struct dma_buf *dma_buf);



static inline u64

panthor_kernel_bo_gpuva(struct panthor_kernel_bo *bo)

{